1. Field of Invention
The present application generally relates to AC induction motors and more specifically to an AC induction motor having increased torque output by increasing the number of poles and increasing the gap between the stator and rotor.
2. Status of the Prior Art
The theory of motor operation can be developed based on the equivalency of electric-to-magnetic-to-mechanical energy exchange. The theory encompasses both the Lorentz Force Equation and the equation for attractive forces. The Lorentz Force Equation is usually invoked for evaluating AC machine performance while the equation for attractive forces evaluates reluctance motor analysis.
The universal law used to explain the operation of an electromotive machine is simply stated as the equivalence of the change in stored magnetic energy dEmagnetic with the change in mechanical shaft energy dEmechanical:dEmagnetic=dEmechanical  Eq. 1                where:        Emagnetic=magnetic energy stored inside the machine (co-energy); and        Emechanical=mechanical energy produced by the machine (shaft energy).        
Magnetic energy exists within a magnetic field because the field requires energy for its formation in the first place. The magnetic field represents the exact amount of energy that was expended for its creation.
The most effective method of storing magnetic energy is with an electromagnetic device known as an inductor. The inductor consists of a coil of n turns surrounding an iron core serving as the magnetic circuit for conducting magnetic flux. The iron core presents low resistance or low reluctance R, to the flow of flux and therefore the core itself contains very little magnetic energy. Consequently, additional reluctance must be added to the magnetic circuit in the form of an air gap in order to increase the energy storage capacitor of the inductor. A relatively small air gap can raise the overall circuit reluctance R by more than ten times. Or in other words, the small gap typically contains over ten times the magnetic energy of the iron core which simply provides the flux conduit for channeling flux through the coil and concentrating flux at the gap.
Additionally, in order to increase the torque of an electric motor, the number of poles can be increased with the penalty of added weight to the motor for a given shape. Furthermore, the addition of poles also decreases the efficiency of the motor. For example, heat dissipation varies as the square of torque. Accordingly, by doubling the torque by adding additional poles, the heat increase will be four-fold.